Question

I want to have my own initialization function, and I want it exit only after onload event, what can I do for it?

var qqq=0;
function init(){
    var requestClient= Ti.Network.createHTTPClient();
    requestClient.open('GET','https://mysite.com/api/123/id/5/friends');
        requestClient.onload = function() {
            alert('loaded');
        };
    requestClient.send();
};
init();
alert(qqq);

Answer 1

Well, you can do that, by making the request synchronous instead of asynchronous. This has unpleasant side-effects on the user’s browsing experience, tending to lock things up during the request, but if you set open‘s third argument to false, it will make it synchronous instead of asynchronous:

var qqq=0;
function init(){
    var requestClient= Ti.Network.createHTTPClient();
    requestClient.open('GET','https://mysite.com/api/123/id/5/friends', false);
                                                           // Here------^
        requestClient.onload = function() {
            alert('loaded');
        };
    requestClient.send();
};
init();
alert(qqq);

A synchronous request will bring the JavaScript execution on the page (at least, and in many browsers rather more than just the JavaScript) to a screeching halt until the network operation completes.

But the usual practice is to have your init accept a callback you call from within the onload handler, as this makes for a much better UX:

var qqq=0;
function init(callback){  // <== Accept a callback
    var requestClient= Ti.Network.createHTTPClient();
    requestClient.open('GET','https://mysite.com/api/123/id/5/friends');
        requestClient.onload = function() {
            alert('loaded');
            callback();   // <== Call the callback
        };
    requestClient.send();
};
init(function() {         // <== Pass the callback into `init`
    alert(qqq);
});

Effective web programming is about embracing the event-driven nature of it. I’d strongly recommend the second example.